Sunn 1200s tech notes

Page 1

TECHNOTES

Fender Musical instruments Corp.
7975 North Hayden Road Scottsdale, Arizona 85258

PRODUCT(S) AFFECTED:

SUNN 12008

SYMPTOMS:

Non-musical distortion, particularly at high volume. Other symptoms vary. depending
on condition.

CONDITION:

By making changes to various circuits. potential problems caused by component
tolerances and/or thermal drift can be avoided. These may include:

1. Operation of compression circuitry can be improved;

2. input level LED operation can be improved;

3. The chance of preamp instability will be reduced;

4. The chance of thermal problems in the power amp will be reduced.

PARTS REQUIRED:

QTY REF. NO. PART NO. DESCRIPTION
4 CH50~53 025821 DIODE, 200PRV SIGNAL FDH4OO (WERE 75PRV)
1 016 051445 CAP CD 500V 22PF 5% (WAS C18)
1 C18 051409 CAP CD 500V 68PF 5% (WAS C16)
1 H184 029596 HES CF 1I4W 620 5% (WAS R185)
1 R185 029592 RES CF 1/4W 439 5% (WAS R184)
1 R282 028153 RES CF 1/4W 75KQ 5% (WAS R283)
1 R283 024997 RES CF 114W 100KQ 5% (WAS R282)

Page 2

TECH NOTE # TN99-1 PAGE: 2 OF 6
PARTS REQUIRED: (cont)
QTY REF. No. PART NO. DESCRIPTION
2 R59.R99 024975 RES CF 1/4w 3.9m 5% (WERE 10m)
2 R108.FI111 024939 RES CF 114w 33m 5% (WERE 47m)
1 R112 024991 RES CF 1/4w 39m (WAS 47m)
2 14194-195 024947 RES CF MW 47:) (MAY BE DAMAGED)
2 moo-201 036960 RES FUSE MF 1/4w 5% 479 T/R (MAY BE DAMAGED)
REQUIRED ACTION:

I) Change CR50-53 to FDH400 ZOOPRV. (Sheet 2 of 4, zones B3, C3)

2) Swap cap values on C16, C18. (Sheet 1 of 4, zones C6, C7)

3) Swap resistor values on R184, R185. (Sheet 2 of 4, zone C3)

4) Swap resistor values on R282, R283. (Sheet 3 of 5, zones C5, D5)

5) Change resistors R89, R99 to 3.9kQ (Sheet 1 of 4, zones D3, D4)

6) Change resistors R108, R111 to 33kg. (Sheet 1 of 4, zones B2, C2)

7) Change resistor R112 to 39kQ. (Sheet 1 of 4, zone Bl)

8) Check resistors R194-R195, and replace as necessary. (Sheet 2 of 4, zones B3, C3)

9) Check resistors R200-R201, and replace as necessary. (Sheet 2 of 4, zones B3, C3)

WARRANTY CLAIM INSTRUCTIONS:

The above modifications should be performed on any SUNN 12008 bass amp that is in
warranty, and exhibiting the above symptoms (and does not have these changes).
Note: Most units have already had these changes installed at the factory - quick
check: look to see if R801, R808, 8. R814 (zone C 5-6 on sheet 4 of service
diagram are 4.7QI7W. If so, this tech-note does not apply) For proper labor
reimbursement, please indicate the Tech Note Number TN99-1 in the Authorization
Code Box (Box # 12) on the Warranty Reimbursement Form. Labor reimbursement = 2

Hours (US. only).